The present invention relates generally to systems and methods for depositing thin films, and more particularly to system and method for depositing optically transparent films of crystalline chromium/carbon/fluorine (Cr/C/F) material.
Conventional methods for plasma-assisted vacuum deposition of metal/polymer or metal/ organic thin films include co-sputtering of polymer/metal composite targets using inert or reactive glow discharges, plasma deposited organometallics, and simultaneous sputter deposition/plasma polymerization. The properties of metal/polymer thin films are significantly influenced by chemical composition and microstructure; for example, Kay et al (Phys. Rev. B Vol.32 No.2 (15 Jul. 1985) 719-732; J.Appl. Phys. 55 (2) (15 Jan. 1984) 370; J. Vac. Sci. Tech. A4 (1) (Jan/Feb 1986 ) demonstrated the effect of incorporating gold into fluorocarbon matrices on electrical and optical properties of deposited films. Changes in electrical resistivity and optical transmission were correlated to and explained by the film microstructure.
Plasma-assisted processing of materials can lead to formation of compounds and structures not obtainable under equilibrium conditions. Chemical composition, crystal structure and physical, electrical and optical properties of plasma synthesized material may be significantly different from equilibrium processed material. For example, incorporating a reactive metal such as aluminum or cobalt into a fluorocarbon plasma polymerizing environment can significantly affect properties of the deposited film. Conductivity of aluminum/fluorine plasma deposited films changed 16 orders of magnitude above and below a critical fluorocarbon/argon gas mixture in the plasma (J. Vac. Sci. Tech. A2 (2) (Apr/Jun 1984 ). Analysis of the films revealed an insulating aluminum-fluorine compound and not a polymeric material; transmission electron microscopy (TEM) of plasma deposited cobalt/fluorine films showed fine particles of metallic Co, Co+CoF.sub.2, and CoF.sub.2 formed as fluorocarbon concentration in the plasma went from below a critical concentration (Co) to well above a critical concentration (CoF.sub.2). Deposition of aluminum and copper by magnetron sputtering in fluorocarbon/argon plasmas showed that by changing power input the amount of metal in the fluoropolymer/metal films could be controlled (Nucl. Inst.. Meth. 212 (1983) 497).
The invention meets a long-felt need in the art by providing system and method for reactive sputter depositing transparent crystalline Cr/C/F thin films onto selected substrate materials using a Cr sputter target and an argon-fluorocarbon (Ar/C.sub.2 F.sub.6) plasma. Film composition was in the (atom percent) range of (35-55)Cr, (20-45)F, and (20-25)C, and was reproducible through selective control of the Ar/C.sub.2 F.sub.6 ratio in the feed gas. Substrate material did not affect composition of the deposited films. The films were optically transparent and were determined by electron diffraction to be crystalline. Binding energies of the Cr, C and F species in the films were shown by x-ray photoelectron spectroscopy (XPS) to be of the Cr-F and C-C type.
It is therefore a principal object of the invention to provide system and method for synthesis and deposition of Cr/C/F films.
It is a further object of the invention to provide system and method for plasma assisted deposition of films of Cr/C/F material.
It is another object of the invention to provide system and method for synthesis and deposition of optically transparent, crystalline Cr/C/F.
These and other objects of the invention will become apparent as a detailed description of representative embodiments proceeds.